1. Field of the Invention
The invention relates generally to the production of man-made composite structural and building products molded from a mat of cellulosic fibers produced by the dry process and molded to include one or more interior depressions. More particularly, the invention relates to the production of a cellulosic core component molded to include one or more interior depressions which can be utilized, for example, in an interior space or void formed by a shell or framework of a building product, particularly as a core component that is adhered between opposed doorskins, said core component having one or more interior depressions shaped to receive depressions molded into the doorskins.
2. Brief Description of Related Technology
The invention is described herein is an improvement over the method and articles described in this Assignee""s U.S. Pat. No. 5,887,402 (""402). The ""402 patent describes a method of manufacturing a core component and then post-press machining or routing one or more interior depressions into at least over major surface of the core component to accommodate interior depressions in the adhered doorskins. In accordance with the present invention, core components are manufactured to include the required interior depressions in the pressing operation to eliminate or substantially reduce any post-press machining.
Man-made boards, such as fiberboard, can be embossed or molded to have three-dimensional shapes and various design and structural features found in natural wood. Types of useful manxe2x80x94man boards are referred to by the following terms, for example: (a) fiberboards such as hardboard (e.g., low-density hardboard), soft board, and medium-density fiberboard and (b) chipboards such as particleboard, medium-density particleboard, and oriented strandboard (xe2x80x9cOSBxe2x80x9d). Composites of these boards are also useful. Such boards, particularly hardboard, have found widespread use in the manufacture of doorskins, which can be glued together or laminated to form a shell which supports or encloses a structure or a frame.
Commonly, doorskins (also referred to as door faces) are molded from a planar cellulosic mat to include one or more interior depressions or contours, such as one or more square or rectangular depressions which do not extend to the outer edge or periphery of the doorskin product. Doorskins often require inclined molded walls having a plurality of contours that include varied curved and planar surfaces. Where the depressions or contours are included on a doorskin product, this can serve to replicate a more expensive natural wood paneled door. For example, doors having two, three, four, five, and six panel designs are commonly produced. The exterior or visible surfaces of the fiberboard also can be embossed with a design that represents a wood grain pattern found in a natural piece of wood.
The principal processes for the manufacture of wood composites such as doorskins and other structural or building products include (a) wet felted/wet pressed or xe2x80x9cwetxe2x80x9d processes, (b) dry felted/dry pressed or xe2x80x9cdryxe2x80x9d processes, and (C) wet felted/dry pressed or xe2x80x9cwet-dryxe2x80x9d processes. The core components of the present invention are manufactured by the dry process.
In the dry process of the present invention, the cellulosic fibers are generally conveyed in a gaseous stream or by mechanical means rather than a liquid stream. For example, the cellulosic fibers may be first coated with a thermosetting resin binder, such as a phenol-formaldehyde resin. The fibers are then randomly formed into a mat by air blowing the resin-coated fibers onto a support member. The mat may optionally be subjected to pre-press drying. The mat, typically having a moisture content of less than about thirty weight percent and preferably less than about ten weight percent, is then pressed under heat and pressure to cure the thermosetting resin and to compress the mat into an integral consolidated structure.
The fiber mats that are made by the dry process do not have as much fiber intertangling of fibrillated fibers as mats made by the wet or wet/dry processes since the dry process fibers are not slurried in water during water drainage, which enhances fiber intermingling and entangling, and are coated with resin prior to substantial fiber intermingling. As a result, dry process mats that are consolidated by heat and pressure are not as strong as wet or wet/dry process consolidated mats and have been found to suffer from surface peeling when relatively thick dry process core components, e.g., one half inch thickness or more, are roll-coated with adhesive for adherence to opposed doorskins.
Fiber mats have been pressed into pre-selected decorative shapes, typically at a thickness of about one-eighth of an inch, to include one or more panels or depressions and/or other contours in the formation of doorskins, as described above. Two doorskin pieces are typically joined together with an adhesive binder, which is placed at least at the contact points along the periphery of the door assembly formed by the doorskins. Because the doorskin pieces are contoured to include one or more depressions surrounded by co-planar stiles and rails, an open, interior space of varying dimensions is formed by the doorskin assembly.
Doorskin pieces are often not used alone, but in conjunction with (surrounding) some other material(s) disposed on an interior space disposed between two opposed doorskins to add support to the final door product. The doorskin pieces often utilize wood framing at or near the perimeter of the assembled doorskin. It is known to use rails and stiles, which, when attached together, can provide additional structural support for the door. Rails can be generally described as horizontally-oriented beams which provide support for the door. Stiles, on the other hand, can be generally described as longitudinal or vertically-oriented beams which provide support for the door. In addition, a lock block is optionally utilized to provide further support for a door handle and/or a locking mechanism (e.g., a so-called xe2x80x9cdead boltxe2x80x9d) at the periphery of the door. The lock block is preferably secured to a stile and/or a rail.
However, although the structure of a man-made composite door product is supported with rails and stiles, often the door still will not perform as well as a natural solid wood door because the interior spaces defined by the opposed doorskins will be substantially hollow or empty. The hollow spaces or voids cause the door to be lighter than is generally preferred. Further, it is often found that the sound insulation provided by such doors may not be satisfactory. Thus, it is often desirable to use a core material (e.g., core pieces or components) to fill these hollow spaces.
A suitable core material should also provide the door product with a desirable weight, for example the weight of a similarly-styled natural solid wood door. A typical, thirty-inch wide solid pine door weighs approximately forty-two pounds. Known core materials and components have the disadvantage, for example, that they often fall far short of the desired weight. In addition, some alternatives to doorskins having a core material (e.g., full thickness particleboard doors) produce a door that is too heavy and/or difficult to manufacture. In addition, a core material should provide the door with a relatively even weight distribution.
The core material should also have characteristics (e.g., size and shape) that allow placement and attachment within the interior spaces formed by the doorskin assembly with very close tolerances required to match the dimensions of the stiles and rails. As described above, doorskins, particularly for paneled doors, are commonly molded to include one or more interior depressions (i.e., on the surface at some distance from the periphery), such as one or more square or rectangular depressions that do not extend to an outer edge of the doorskin. These surface depressions create varying depths (measured from the front face to the back face of the door) of the interior void formed by a pair of assembled doorskins. When placing a core material or component on the interior of the doorskin assembly, it is therefore necessary to compensate for the varying depth of the interior void.
In the past, core materials made of corrugated cardboard and/or paper have been used. However, it has been found that sometimes the sound insulation provided by doors using such core materials may not be satisfactory. This Assignee""s U.S. Pat. No. 5,887,402 describes contoured core components made from wood fibers which solved many of the problems associated with the void space, or resulting from inadequate core materials, that existed prior to the ""402 invention. However, in accordance with the ""402 patent, time- and labor-intensive post-press machining or routing of the major surfaces of the core components to accommodate depressions formed in adhered doorskins. This process of machining or routing depressions into major surfaces of the core components has caused major plant dusting problems and has caused the final door product to be too expensive, substantially reducing the commercial success of the composite core component embodiment wherein the core components are disposed between spaced doorskins.
In accordance with the present invention, a variety of manufacturing problems have been overcome in the manufacture of core components since the ""402 invention, particularly in processing depressions into the core material and in pressing the fibrous mat to form core components having consistent caliper measurements, in a unitary, non-laminated structure, to match the caliper of core component-adjoining stiles and rails, to allow for the manufacture of core components that include interior depressions formed directly in the core components in the consolidation press in order to eliminate or substantially reduce post-press surface-forming steps, such as machining, while providing core material depressions contoured to receive the adjacent doorskin depressions.
It is an object of the invention to overcome one or more of the problems described above, in the manufacture of wood-fiber, contoured core components for any use described herein, particularly for core components disposed between spaced doorskins.
Accordingly, the methods and articles described herein provide a core component that can provide various beneficial properties to various building components, such as doors. The core component is a contoured article having two major exterior surfaces defining respective front and rear sides thereof. There is at least one molded depression or contour in at least one, and preferably both major planar surfaces, wherein the rear side of each core component is preferably molded to be the mirror image of the front side. In one embodiment, the depressions each include (a) first and second inclined depression walls extending downwardly from the major plane and (b) a depression bottom extending between the inclined depression walls.
According to a preferred embodiment, a door core component is adapted, by molding, for placement on the interior of (sandwiched between) a pair of doorskins defining a core component-receiving interior space or void, so as to provide a composite door with various improved characteristics, including, for example, beneficial weight, strength (e.g., rigidity), sound insulation, and fire insulation properties. The preferred core components are made of a composite soft board material, having a specific gravity less than about 0.4, compressed from a dry process mat having a basis weight of about 0.9 lb./ft2 to about 3.0 lb./ft2 after wetting at least one, and preferably both major surfaces of the mat to contain an average of at least 2% by weight more moisture in wetted major surface layer(s), when placed into the mold cavity, than the average moisture content at the center of the thickness of the mat, based on the dry weight of the mat. Said surface layers are hereby defined to consist of 10% of the thickness of the mat when placed in the mold cavity, measured from, and perpendicular to, the wetted surface.
The methods and articles described herein also provide a rigid building or structural member having one or more interior spaces or voids, such as a door product, utilizing the inventive core component. The shell or exterior of the building member, e.g., doorskins, as well as the core component, are preferably made of a composite cellulosic material containing at least 80%, preferably at least 85%, cellulosic fibers refined from wood, e.g., wood chips. The core component can be secured on the interior of the building member with an adhesive. The invention also provides a process of producing such a building member by the dry process, in a method that is improved over that described in U.S. Pat. No. 5,887,402.
In one embodiment, the core component includes a feature wherein a single design of core component can be utilized in various styles of building member shells. This feature includes providing contours or depressions to the core component, such that a core component having a single design can fit into the hollow spaces or voids found, for example, in multiple styles of paneled (e.g. six-paneled) and/or contoured doors.
Further objects, aspects and advantages of the methods and articles described herein will be apparent to those skilled in the art from the following detailed description, taken in conjunction with the drawings and the appended claims.